The present invention relates to improvements in a wire electric discharge machine to conduct machining on a workpiece when electric power for machining is supplied between an electrode and the workpiece.
First of all, the formation of a recess portion on a machined face of a workpiece by electric discharge machining will be explained below. FIG. 6 is a schematic illustration showing a relative movement path, which will be referred to as an electrode path in this specification hereinafter, formed between a wire electrode and workpiece in the case of wire electric discharge machining. In the drawing, reference numeral 1 is a workpiece, reference numeral 2 is a machined profile portion of an electrode path to be machined to an objective profile (This machined profile portion of the electrode path will be referred to as a profile portion in this specification hereinafter.), reference numeral 3 is a point at which a machining start hole is formed (This point will be referred to as a machining start point in this specification hereinafter.), reference numeral 4 is an approach path portion of the electrode path formed from the machining start point 3 to the profile portion 2 (This approach path portion will be referred to as an approach portion in this specification hereinafter.), and reference mark O is a connection point of the profile portion 2 with the approach portion 4 (This connection point will be referred to as an approach point in this specification hereinafter.). FIG. 7 is an enlarged view of the neighborhood of approach point O shown in FIG. 6. Like reference characters are used to indicate like parts in FIGS. 6 and 7. In FIG. 7, reference numeral 5 is a wire electrode, and reference numeral 6 is a recess portion.
As well known, wire electric discharge machining is a method of machining in which the wire electrode 5 is used as if it were a fretsaw to cut out the workpiece 1. In the process of wire electric discharge machining, not only the profile portion 2 but also the approach portion 4 is machined as shown in FIG. 6.
In the profile portion 2 of usual wire electric discharge machining, consideration must be given to a radius of the wire electrode 5, electric discharge gap and allowance necessary for finishing. Therefore, a path is set which is distant from the profile to be machined by a predetermined distance which is referred to as an offset, and electric discharge machining is conducted when the center of the wire electrode 5 is moved along this offset path. As shown in FIG. 7, the wire electrode 5 starts at the machining start point 3 and passes through the approach portion 4 and then moves from approach point O to the profile portion 2 and makes a round of the profile portion 2 and then returns to the machining start point 3 via the approach point O and the approach portion 4.
When the wire electrode 5 moves as described above and makes a round of the profile portion 2, the wire electrode 5 passes through the profile portion 2 only once except for approach point O, that is, the wire electrode 5 passes through only approach point O twice. When the electrode 5 passes through approach point O for the second time, the portion of the workpiece 1 to be removed has already been removed. Therefore, when the electrode 5 passes through approach point O for the second time, electric discharge is generated on the face which has already been machined, and overcutting is caused on the machined face. Accordingly, the recess portion 6 is formed in the neighborhood of approach point O on the machined face of the workpiece 1.
In the case of conducting wire electric discharge machining on a workpiece so as to make a metallic mold for resin molding, resin molding is conducted with the metallic mold by transferring the profile formed by electric discharge machining. Therefore, when the recess portion 6 exists on the machined face of the metallic mold which is machined as a workpiece of wire electric discharge machining, an unexpected pattern is formed on a resin product made by this metallic mold. In order to solve this problem, it is necessary to form a uniform profile of the metallic mold having no recess portion 6. Therefore, it is necessary to remove the recess portion 6, which has been formed on the machine face of the workpiece as shown in FIG. 7, by after-machining such as wire electric discharge machining. In this case, it is necessary to remove the entire volume of a hatched portion in FIG. 8 from the workpiece 1.
As a method of suppressing the generation of the recess portion 6, Japanese Unexamined Patent Publication No. 4-189421 discloses a wire electric discharge machining method. According to this method, as shown in FIG. 9, the first approach point OA and the second approach point OB are set on the profile portion 2, and the approach path is connected with these two approach points, that is, the approach portions 4A and 4B are connected with these two approach points, and the electric discharge machining program is changed so that an electrode path in the profile portion between approach points OA and OB in FIG. 9 can be deleted. In this way, the electrode path is changed as shown in FIG. 9.
Further, as a method of suppressing the generation of the recess portion 6, International Patent Application No. PCT/JP01/09577 discloses an invention. According to this invention, two approach points are not set, and the electrode path is formed in the same manner as that shown in FIG. 7. When a distance between approach point 0, at which the approach portion 4 and the profile portion 2 of the electrode path are connected with each other, and the center of the wire electrode 5 in the profile portion 2 is in a range in which a machining volume of the workpiece 1 per unit moving distance of the wire electrode 5 is decreased, electric discharge machining is conducted when an intensity of energy of machining per unit moving distance of the wire electrode 5 is decreased.
In the case where the workpiece is a metallic mold used for resin forming, when the recess portion 6 shown in FIG. 7 is not formed but the protruding portion 7 shown in FIG. 10 is formed, it is unnecessary to remove the entire volume of a hatched portion in FIG. 8, that is, only the protruding portion 7 shown in FIG. 10 may be removed. Therefore, the time required for after-machining can be greatly reduced. In this way, the profile of a portion in the neighborhood of approach point O of the workpiece 1 may be positively formed into a protrusion in some cases.
In the case where the workpiece is a metallic die used for press forming, if the protruding portion 7 shown in FIG. 10 is formed in the neighborhood of approach point O of the workpiece 1, the protruding portion 7 collides with the punch in the process of press forming and the metallic die is damaged. Therefore, it is necessary to remove the protruding portion 7, however, in the case of a metallic die used for press forming in which after-machining is unnecessary, a recess portion like the recess portion 6 shown in FIG. 7 may exist.
The invention disclosed in Japanese Unexamined Patent Publication No. 4-189421 and the invention disclosed in International Patent Application No. PCT/JP01/09577 have a predetermined effect to suppress the formation of the recess portion 6 described above, however, it is impossible to desirably adjust the profile of a portion in the neighborhood of the approach point on a machined face of a workpiece.
The present invention has been accomplished to solve the above problems. It is an object of the present invention to provide a wire electric discharge machine capable of adjusting a profile of a portion in the neighborhood of an approach point on a machined face of a workpiece so that it can be formed into a desired profile.
The present invention provides a wire electric discharge machine in which a wire electrode and workpiece are relatively moved from each other by a drive means and energy for machining is supplied between the wire electrode and workpiece by a machining electric power supply means so that the workpiece is machined by electric discharge generated between the wire electrode and workpiece, the wire electric discharge machine comprising: a profile directing means for directing a profile of a portion in the neighborhood of an approach point, which connects an approach path portion with a machining profile portion of the relative movement path on a machined face of the workpiece, to be a desirable profile such as a protruding profile or recess profile according to the use of the workpiece; and an adjusting means for adjusting a profile of the portion in the neighborhood of the approach point according to the direction value directed by the profile directing means.
In the wire electric discharge machine of the present invention, the adjusting means is a machining energy adjusting coefficient setting means for increasing and decreasing energy for machining.
The present invention provides a wire electric discharge machine in which a wire electrode and workpiece are relatively moved from each other by a drive means and energy for machining is supplied between the wire electrode and workpiece by a machining electric power supply means so that the workpiece is machined by electric discharge generated between the wire electrode and workpiece, the wire electric discharge machine comprising: a machining energy adjusting means for suppressing the formation of a recess portion in the neighborhood of the approach point on the machined face of the workpiece by reducing an intensity of machining energy per unit moving distance of the wire electrode when a distance between the approach point, at which the approach path portion and the machining profile portion of the electrode path are connected with each other, and the center of the wire electrode in the machining profile portion is in a range in which a machining volume of the workpiece per unit moving distance of the wire electrode is decreased; a profile directing means for directing a profile of a portion in the neighborhood of an approach point on the machined face of the workpiece to be a desirable profile such as a protruding profile or recess profile according to the use of the workpiece; and a machining energy adjusting coefficient setting means for adjusting a profile of a portion in the neighborhood of the approach point on the machined face of the workpiece according to a direction value directed by the profile directing means, wherein when a machining energy setting value of the machining energy adjusting means for suppressing the formation of a recess portion in the neighborhood of the approach point on the machined face of the workpiece is increased and decreased by the machining energy adjusting coefficient setting means, a desired protruding profile or recess profile is formed in a portion in the neighborhood of the approach point on the machined face of the workpiece.
The present invention provides a wire electric discharge machine in which a wire electrode and workpiece are relatively moved from each other by a drive means and two different approach points (a first approach point and a second approach point) to connect an approach path portion with a machining profile portion of the relative moving path are set and a portion of the relative moving path of the machining profile portion between the two approach points is deleted so that electric discharge machining is conducted on a machining profile portion of the relative moving path from the first approach point to the second approach point, the wire electric discharge machine comprising: a profile directing means for directing a profile of a portion in the neighborhood of an approach point to be a desirable profile such as a protruding profile or recess profile according to the use of a workpiece; and an approach point interval adjusting means for adjusting an interval between the first approach point and the second approach point according to a direction value given by the profile directing means.
Since the wire electric discharge machine of the present invention is composed as described above, it is possible to provide an effect that a profile of a portion in the neighborhood of an approach point on a machined face of a workpiece can be adjusted to be a desired profile according to the use of a workpiece.